Is emission-less propulsion possible? I believe it is...

[mikelewis]

30. And to prove that... here's all the math...

can we estimate all the variables, place the spaceman in a suit with the double barrel, weigh him, fire off the two rounds, calculate his speed after the firing, figure out the resistance level and how much to remove from the momentum of the slugs... best assumptions here and then add that momentum to the current momentum of the astronaut please... best guesses here are fine

ChatGPT
To make a rough estimation of the scenario you're describing, we need to consider several factors and make a number of assumptions. Let's break it down step by step:

Mass of the Astronaut and Gear:

Assume the astronaut's mass (including the spacesuit) is around 100 kg (a round figure for simplicity, though spacesuits can be quite heavy).
The mass of a double-barreled shotgun can vary, but let's assume it's around 4 kg.
Shotgun Recoil:

The recoil of a shotgun depends on the specific ammunition used. Let's assume a standard 12-gauge shotgun shell, which typically has a muzzle velocity of about 400 m/s and a mass of about 28 grams (0.028 kg) per slug.
When both barrels are fired, the total mass of the projectiles is 0.056 kg.
Calculating Recoil Velocity:

According to the conservation of momentum,
�gun - �gun + � slugs ⋅ �slugs =0m
gun
​
⋅v
gun
​
+m
slugs
​
⋅v
slugs
​
=0, where
�
gun
m
gun
​
is the mass of the astronaut and gear,
�
gun
v
gun
​
is the recoil velocity,
�
slugs
m
slugs
​
is the mass of the slugs, and
�
slugs
v
slugs
​
is the velocity of the slugs.
Effect of Bullets Redirected Back at the Astronaut:

If the bullets are redirected back at the astronaut and hit him, their momentum would be added to his. However, since the bullets would lose energy due to sound and heat, not all their momentum would be transferred. For simplicity, let's assume 90% of the momentum is transferred back.
The bullets and astronaut are moving in the same direction after firing, so the momentum adds up, not cancel out.
Let's perform the calculations with these assumptions.

Finished analyzing
python
Copy code
# Given data and assumptions
mass_astronaut_gear = 100 # in kg (astronaut + spacesuit)
mass_shotgun = 4 # in kg
mass_slugs = 0.056 # Total mass of two slugs in kg (0.028 kg each)
velocity_slugs = 400 # Muzzle velocity in m/s

# Total mass of astronaut and gear
total_mass = mass_astronaut_gear + mass_shotgun

# Conservation of momentum to find recoil velocity
# m_gun * v_gun + m_slugs * v_slugs = 0 => v_gun = -(m_slugs * v_slugs) / m_gun
recoil_velocity = -(mass_slugs * velocity_slugs) / total_mass

# Assuming 90% of the slugs' momentum is transferred back to the astronaut
momentum_transfer_percentage = 0.9
effective_momentum_slugs = momentum_transfer_percentage * mass_slugs * velocity_slugs

# The effective recoil velocity after momentum transfer (adding because in the same direction)
effective_recoil_velocity = recoil_velocity + (effective_momentum_slugs / total_mass)

recoil_velocity, effective_recoil_velocity

Result
(-0.2153846153846154, -0.021538461538461562)
Based on the assumptions and calculations:

The initial recoil velocity of the astronaut and gear after firing the double-barreled shotgun is approximately
−
0.215
−0.215 m/s (negative sign indicating direction opposite to the bullet's motion).
After the bullets are redirected back and 90% of their momentum is transferred to the astronaut, the effective recoil velocity is approximately
−
0.022
−0.022 m/s.
This means that initially, the astronaut is propelled backwards at about 0.215 m/s. After the bullets hit him and transfer their momentum, his speed is reduced to around 0.022 m/s in the same direction. The significant reduction in speed is due to the partial transfer of momentum from the slugs to the astronaut. ​​

User
That's fine but they would still be moving and let's assume repeated firings... how fast in mph after 1 shot, 5 shots, 100 shots...
ChatGPT
To calculate the speed of the astronaut in miles per hour (mph) after multiple shots, we'll use the effective recoil velocity we calculated earlier. We'll then scale this velocity with the number of shots and convert it to mph.

The effective recoil velocity we calculated is approximately
−
0.022
−0.022 m/s per shot. Let's calculate the speed for 1, 5, and 100 shots:

Speed After 1 Shot:

The speed is simply the effective recoil velocity.
Speed After 5 Shots:

The speed is 5 times the effective recoil velocity.
Speed After 100 Shots:

The speed is 100 times the effective recoil velocity.
We'll then convert these speeds from meters per second (m/s) to miles per hour (mph). The conversion factor is 1 m/s ≈ 2.237 mph. Let's do the calculations.

Based on the calculations:

After 1 shot, the astronaut would be moving at approximately
−
0.048
−0.048 mph.
After 5 shots, the speed would increase to about
−
0.241
−0.241 mph.
After 100 shots, the astronaut would be moving at roughly
−
4.82
−4.82 mph.
These speeds are cumulative, assuming each shot adds the same amount of velocity and that all other conditions remain constant. The negative sign indicates the direction of motion is opposite to the initial bullet direction. Remember, these are rough estimates based on a simplified model of the situation. ​​

User
So as a propulsion method, this would only be viable if he only had two slugs and lots of powder...
ChatGPT
Yes, using a shotgun as a propulsion method in space, as depicted in your scenario, would be more effective if the astronaut has only a few slugs and a lot of gunpowder. This is due to several key factors:

Limited Increase in Speed per Shot:

As the calculations show, each shot only imparts a relatively small increase in speed (a few hundredths of a mph per shot). This means that to achieve significant speeds, a large number of shots would be required.
Practicality of Carrying Ammunition:

Carrying a large number of slugs would be impractical due to space and weight constraints. However, if the astronaut could reuse the same slugs with additional gunpowder, this would reduce the need for carrying a large amount of ammunition.
Efficiency of Momentum Transfer:

In your scenario, bending the barrels to redirect the slugs back towards the astronaut and then reusing them is a creative way to maintain the supply of slugs. However, the efficiency of this process is crucial. Realistically, each redirection and impact would result in some loss of energy and momentum, making the process less efficient over time.
Safety and Control:

Using a shotgun for propulsion in space poses significant safety risks, especially considering the need to precisely aim the weapon to control the direction of movement. Additionally, the impact of the slugs, even if the suit is bulletproof, could cause harm or damage the suit.
In summary, while the concept is intriguing and highlights some interesting physics principles, it's not a practical method for propulsion in space with current technology and safety standards. More conventional methods like chemical rockets or ion thrusters are currently more viable for space propulsion.